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25 //
26 // G4DataInterpolation
27 //
28 // Class description:
29 //
30 // The class consists of some methods for data interpolations and
31 // extrapolations. The methods based mainly on recommendations given in the
32 // book: An introduction to NUMERICAL METHODS IN C++, B.H. Flowers,
33 // Claredon Press, Oxford, 1995.
34
35 // Author: V.Grichine, 03.04.1997
36 // --------------------------------------------------------------------
37 #ifndef G4DATAINTERPOLATION_HH
38 #define G4DATAINTERPOLATION_HH 1
39
40 #include "globals.hh"
41
42 class G4DataInterpolation
43 {
44 public:
45 G4DataInterpolation(G4double pX[], G4double pY[], G4int number);
46 // Constructor for initializing data members.
47
48 G4DataInterpolation(G4double pX[], G4double pY[], G4int number,
49 G4double pFirstDerStart, G4double pFirstDerFinish);
50 // Constructor for cubic spline interpolation. It creates fSecond Deivative
51 // array as well as fArgument and fFunction.
52
53 ~G4DataInterpolation();
54 // Destructor deletes dynamically created arrays for data members: fArgument,
55 // fFunction and fSecondDerivative, all have dimension of fNumber.
56
57 G4DataInterpolation(const G4DataInterpolation&) = delete;
58 G4DataInterpolation& operator=(const G4DataInterpolation&) = delete;
59 // Copy constructor and assignement operator not allowed.
60
61 G4double PolynomInterpolation(G4double pX, G4double& deltaY) const;
62 // This function returns the value P(pX), where P(x) is polynom of fNumber-1
63 // degree such that P(fArgument[i]) = fFunction[i], for i = 0, ..., fNumber-1.
64
65 void PolIntCoefficient(G4double cof[]) const;
66 // Given arrays fArgument[0,..,fNumber-1] and fFunction[0,..,fNumber-1], this
67 // function calculates an array of coefficients.
68 // The coefficients don't provide usually (fNumber>10) better accuracy for
69 // polynom interpolation, as compared with PolynomInterpolation() function.
70 // They could be used instead for derivate calculations and some other
71 // applications.
72
73 G4double RationalPolInterpolation(G4double pX, G4double& deltaY) const;
74 // The function returns diagonal rational function (Bulirsch and Stoer
75 // algorithm of Neville type) Pn(x)/Qm(x) where P and Q are polynoms.
76 // Tests showed the method is not stable and hasn't advantage if compared
77 // with polynomial interpolation.
78
79 G4double CubicSplineInterpolation(G4double pX) const;
80 // Cubic spline interpolation in point pX for function given by the table:
81 // fArgument, fFunction. The constructor, which creates fSecondDerivative,
82 // must be called before. The function works optimal, if sequential calls
83 // are in random values of pX.
84
85 G4double FastCubicSpline(G4double pX, G4int index) const;
86 // Return cubic spline interpolation in the point pX which is located between
87 // fArgument[index] and fArgument[index+1]. It is usually called in sequence
88 // of known from external analysis values of index.
89
90 G4int LocateArgument(G4double pX) const;
91 // Given argument pX, returns index k, so that pX bracketed by fArgument[k]
92 // and fArgument[k+1].
93
94 void CorrelatedSearch(G4double pX, G4int& index) const;
95 // Given a value pX, returns a value 'index' such that pX is between
96 // fArgument[index] and fArgument[index+1]. fArgument MUST BE MONOTONIC,
97 // either increasing or decreasing. If index = -1 or fNumber, this indicates
98 // that pX is out of range. The value index on input is taken as the initial
99 // approximation for index on output.
100
101 private:
102 // pointers to data table to be interpolated for y[i] and x[i] respectively
103 G4double* fArgument = nullptr;
104 G4double* fFunction = nullptr;
105
106 G4double* fSecondDerivative = nullptr;
107
108 G4int fNumber = 0; // the corresponding table size
109 };
110
111 #endif
112